Scientists Reveal New “Raptor” Dinosaur from North America

Scientists Reveal New
“Raptor” Dinosaur from North AmericaNew cousin of Velociraptor lived with T. rex and Triceratops

(Toronto, Ontario, December 16, 2013) – Scientists have named a new species of a small, meat-eating dinosaur (‘raptor’) based on newly discovered fossils from Montana, USA. Acheroraptor (ACK-ear-oh-RAP-tor) temertyorumis the youngest known dromaeosaurid, or “raptor” dinosaur. A close cousin of Velociraptor, it was approximately three metres (nine feet) long and weighed about 40 kilograms (90 pounds). Research describing the new species is published in the latest issue of Naturwissenschaften.

The new dinosaur discovery is based on a pair of associated upper and lower jaws from the Hell Creek Formation of Montana. Acheroraptor walked on two legs and was relatively large for a “raptor”, with a long-snouted skull and dagger-like ridged teeth. Due to its close relationship to birds and other feathered dinosaurs, it was likely covered in feathers.

Acheroraptor means “Acheron Plunderer” and is derived from Acheron, the River of Pain in the underworld of ancient Greek mythology, and the Latin word raptor, meaning robber or plunderer, acknowledging the Hell Creek Formation origin of the fossils. The specific name was chosen to honour James and Louise Temerty, for their outstanding service and contributions to the Royal Ontario Museum (ROM) and their enthusiastic support of its palaeontology initiatives.

Acheroraptor was one of the last non-avian dinosaurs. It lived 67 to 66 million years ago in western North America, in a community that included the famous mega-predator Tyrannosaurus rex and the three-horned plant-eater Triceratops. However, among dromaeosaurs, the jaw bones of Acheroraptor compare more closely to those of Velociraptor and other long-snouted Asian species than those of older North American species.

"Acheroraptor gives us a more complete picture of the ecosystem in North America just before the great extinction that marked the end of the Age of Dinosaurs," says lead author Dr. David Evans, Curator of Vertebrate Palaeontology at the ROM. “The close evolutionary relationship of Acheroraptor to a small group of late-occurring Asian species that includes Velociraptor suggests migration from Asia continued to shape North American dinosaur communities right up until the end of the Cretaceous period."

“We have had scanty evidence for more than a century that “raptors” lived with Tyrannosaurs rex until the end of the Cretaceous,” says Dr. Phillip Currie, professor at the University of Alberta. “But the absence of clearly identifiable dromaeosaurid fossils has been perplexing to the dinosaur-hunters who have worked in the Hell Creek area, which has otherwise produced abundant fossils.”

The unique ridged teeth of Acheroraptor have been recognized for decades, but scientists did not have more complete material allowing them to understand the evolutionary relationships of the Hell Creek dromaeosaur until now. “The most exciting aspect of the specimen is the teeth,” says co-author Derek Larson, a Ph.D. student at the University of Toronto. “We now know that those teeth all belong to the same animal, and we now know enough about what that animal looks like to distinguish it as its own species.” Analysis of Acheroraptor’s teeth in the context of a larger sample of small meat-eating dinosaur teeth suggests a decline in dromaeosaur diversity in North America just before the end-Cretaceous extinction event.

Acheroraptor was described by a team of palaeontologists including Dr. David Evans, of the Royal Ontario Museum; Dr. Philip J. Currie, professor at the University of Alberta; and Derek Larson, a graduate student at the University of Toronto who studies under Evans.

“We are proud to support ground-breaking palaeontology research initiatives at the ROM, which provide fascinating insights into our history and the world we live in,” says James Temerty. These newly discovered original fossils of Acheroraptor are on display through the holiday season in the James and Louise Temerty Galleries of the Age of Dinosaurs on Level 2 of the ROM’s Michael Lee-Chin Crystal.

Full Reference: Evans, D. C., D. Larson, and P. J. Currie. 2013. A new dromaeosaurid (Dinosauria: Theropoda) with Asian Affinities from the latest Cretaceous of North America. Naturwissenschaften 100 (11): 1041-1049. Available online.